It's so large that, if the head gasket fails, the boost pressure will escape, and there are almost no cracks or holes.
Nevertheless, you should keep an eye on the oil level and the coolant level.
Due to the gray smoke: it's possible that your crankcase pressure is too high and your oil separator is no longer working properly.
"That would explain the leaking seals and the gray smoke..."
I'm currently experiencing the same problem. The boost pressure, set to 1.3 bar, drops to 1.1 bar after just one second. If I briefly release the accelerator and then press it again, the boost pressure will increase to 1.3 bar for about one second – but the overboost goes above 1.5 bar.
It can't be the turbo itself, since there is pressure being generated. The variable geometry turbo (VTG) was at least working smoothly recently.
Wird mal am WE noch mal die VTG checken, und vor allem die Soll/Ist Daten des MSG mitloggen. Let's see.
Right now, I can't go full speed because it would get too dark in the back.